Negative resistance



May 2l, '1935- v E. H. YoNKERs, JR 2,002,238

` NEGATIVE RESLSTANCE Filed Jury 22, 195o l l s l l l i PatentedMay-*21, 1935 UNITED STAT-s PATENT'. oFFlcE 2.002.238 f g l NEGATIVEna'srs'ranca adware n. :minima` Jr.,carimo, m. -iippucauon Julyfzz,i930, semi Naseem somma. (ci. 25ms) 'I'he present invention relates ingeneral to electrical circuits, particularly those of the type known asnegative resistance'circuits for producing oscillating currents, thepresent inventiony 5 employing a function of the electrons thrown oilfrom an incandescent cathode for this purpose.

One of the objects ofy my invention is to provide a device havingnegative electrical resistance characteristics, that is, a devicewherein the current varies inversely with the applied potentlal, and'-wherein this variation ofcurrent is attained by regulation of thevelocity of flow of. elewctrons between the various electrodes of thePriorart devices --known to me wherein nega-A phenomena is employedforessential. to, the attainment of the functions of this device.

Further objects of this invention reside in the provision of a unitarystructure capable of convenientinstallation in electrical circuits forproducing the desired results, and for carrying out the method hereinvolved; the provision of a system and method of producing electricaloscillations vreferred to whe'rein the various electrodes of the deviceare appropriately mounted in a highlyl evacuated -container convenientlyyof transparent material, suchasglass or the like, and provided withsuitable lead-in wires capable of connectionas desired in the circuit inwhich the device is to be used.

The foregoingand such anna-.objects and advantages which may appear orbe pointed out as this description proceedmare attained in a structuralembodiment ofl the invention for carrying 40" the method and systemvinto eiiect, illustrated in the accompanyinggdrawing wherein: y

Figure 1 is a composite view in longitudinal and transverse sectionillustrating one form( of a device for carryingL out the invention; j

Figure 2 is a diagram illustrating the current characteristics oi one ofthe devices otthis invention; f

Figure 3 is a diagrammaticRview of an electrical vcircuit incorporatingthe featuresof this invention. l

Referring now'more particularly t9 th drawing and ilrst to Figure 1, Ihave illustrated a highly evacuated envelope i, which may be formed of atransparent material, such k,as glass, and includes the enlargedibulbportion I, pro- .REISSUED vided wimrsduced ends 1 and s. formed withuiwardly directed axially aligned pedestals l and 9a, which serve assupporting elementsforthe' lead-in wires and electrodes hereinafterdescribed. .l

Extending through and `supported by the pedestal 9 I provide aillamentary cathode III, whose lead-in conductors II are connected so asto supply current for heating the cathode I0 to incandescence. In thestructural embodiment shown in Figure 1 for convenience I provide a-grid I2, which latter ismounted preferably on the longitudinal axis ofthe device and is helical inV form, that is, is formed of a coiled wirewith the convolutions thereof slightly spaced apart. The grid issupported on its conductorwire Il, which latter extends through thepedestal 9a and is connected in an electrical circuit as will behereinafter described.

The grid |27 is itself surrounded by a system of electrodes includingthe inner electrode I4 composed of the disks I5, which are thusperpendicular to the axis of the grid. The electrode Il is provided withthe collar I6 surrounding and supported by the pedestal 9, a lead-inwire Il being connected to said collar.

A fourth electrode is provided which comprises an annular plate I8,supported by arms I! ilxediy secured to a ring 20 surrounding andsupported by the pedestal 8a. A lead-in wire 2I is connected to the ring20. It will be understood that the electrode I8 isin the natureofacylinder whose axis is coincident with the axis of the device.

The operating characteristics oi the device are determined by thegeometry of the disc system or third electrode. The envelope 5 should beexhausted to such a degree of vacuum that no appreciable current iscarried by gaseous ions when the required potentials are -applied to thedevice.

If the cathode I0 is connected to earth and heated to incandescence anda positive potential is applied to the grid I2 there will be a iiow of lelectrons from cathode Ilto grid I2. Some of these electrons will passthrough the openings in the coiled portion or the grid and move towardthe plates I5 of the third electrode Il.V Thelr velocity `upon reachingthe boundaries of the third electrode will be determined by thepotential ot that electrode with respect to the cathode. Thus, a streamof electrons will flow between the dises I! of the third electrode witha velocity determined by the potential of said electrode. v

, Due to their mutual repulsion the electrons comprising this streamdevelop an additional u ing a negative current of electricity to flowfrom the third electrode I4. The magnitude of this current is an inversefunction of the velocity of the stream of electrons -which enters thespace be-A tween the discs I5 of the third electrode provided the fourthelectrode VI8 is maintained` at some suitable positive potential. Thisis because at high velocities the time required for the individualelectrons to pass between the discs is small and their displacementvtward the discs is therefore small, whereas, at low velocitiestheir'time between the discs is sufficiently long to permit a. largeportion of them to migrate to the discs. Thus, when the potential of thethird electrode is h ighthe current to it is small and the current tothe fourth electrode is large and when the potential of the thirdelectrode is low the current to it is large and that to the fourthelectrode is small.

These characteristics can best be understood by reference to the curvesshown in Figure 2 in which the ordinates represent electron currents tothe third and fourth electrodes I4 and I8 and the absciss represent thepotential of the third electrode I4. Curve A represents the current-po--tential characteristic of the third electrode and curve B ,representsthe, corresponding variations in current to the fourth electrode whenthe potential of the third electrode is varied, the potential of thefourth electrode being fixed at some suitable positive value. Theportion of the curves between the limits R and S indicates the useful oroperating range of the device. Between these limits the slope of thecurrent-potential characteristic of the third electrode is negative andthe slope of the corresponding current characteristic of the fourthelectrode is positive but equal. in value to that of the thirdelectrode. Thus, the third electrode provides negative'resistance andthe fourth electrode provides a source of current variations equal inamplitude to variations which occur in the circuit of thethird electrodewithout appreciably loading said circuit.

In Figure 3 I have illustrated a system in which a negative resistancedevice such as I have described above may be used to generatealternating currents of any desired frequency from a source of directcurrent. The electron discharge device 5 is constructed as shown inFigure 1. l A battery l22 provides current for heating the lamentarycathode Il) and a battery 23 is employed to impress a constant positivepotential upon'the grid I2.

'I'he fourth electrode I8 is also connected to battery 23 through theprimary winding 25 of a transformer 26. The'secondary winding .21 ofsaid transformer is included in some work circuit such as the antenna 28of a radio transmitting system.

The circuit connecting the third electrode I4 to the cathode .I 0includesal suitable portion of battery 23 and a resonant circuitconsisting of inductance 29, capacitance 30.and resistance 3|.

The point 31 at which the thirdelectrode is connected to battery 23 isso selected that the positive potential impressed upon the electrode I4lies within the operating range of the device, that is,

between the limits It and S shown in Figure 2.

of the current-potential characteristic, is less than the equivalentparallel resistancel of the resonant circuit, oscillations or pulsatingcurrents will be generatedin this circuit. Current variations 0f similaramplitude occur ln the circuit which includes electrode I8 as describedabove and thus supply energy in the form of alternating currents to thework circuit.

The frequency of the oscillations generated is determined entirely bythe constants of the resonant circuit which is associated with the thirdelectrode. Variations in-the nature of the work circuit have very littleeifect upon the generated frequency.

Since my' device depends for its operation only upon the geometry oftheelectrodes comprising it and upon the fundamental properties of an'electron stream, its characteristics can be varied to meet therequirements of specific applications by properly designing the form ofthe third elec' trode. In this respect my device offers distinctadvantages over previously employed negative resistance devices basedupon gas ionization or secondary emission effects, which have been foundto be somewhat erratic in their operation and critical as tooperating'potentials.V

Having thus described my invention and illusing a highly evacuatedreceptacle, an electron emitting cathode therein, a grid'adjacent tosaid cathode, said cathode and grid being connected to a source ofdifference potential, a third eleotrode in said receptacle comprisingspaced plates lying adjacent to the path of electron emission from saidcathode, said third electrode being connected through a resonant circuitto a portion of said source of diilerence of potential 'so as to be atpositive potential with respect to said cathode, and a fourth electrodein said receptacle connected to a portion of said source of potential ofgreater .positive potential than that impressed n said third electrodeand forming part of an external work circuit, electrons emitted fromsaid cathode passing between the plates of lsaid third electrode intheirpath to the fourth electrode, whereby the current ow between saidelectrodes is varied inversely with the velocity of the electrons.

- 2. In a device of the character described, in combination, avthermionic device comprising a highly evacuated envelop, an electronemitting cathode-in said envelop, a grid adjacent to said cathode, andan anode in said envelop, a negative resistance element interposedbetween the grid and said anode and comprising a plurality ofsubstantially parallel inter-connected spaced metal plates lyingparallel to the electron streamfrom saidcathode to said anode, and'meansfor im` the work` Q

